Agriculture & Climate change, Australia (Commonwealth Union) – In a groundbreaking publication featured in Nature recently, researchers from the University of Sydney have shed light on the remarkable journey of pesticides after their initial application in agriculture, uncovering significant environmental implications for diverse ecosystems.
Globally, an astonishing three million tonnes of agricultural pesticides are used annually, yet the fate of these chemicals remains largely unknown once they are deployed in the fields. This comprehensive global study, examining 92 of the most commonly used agricultural pesticides, has unveiled a startling discovery: approximately 70,000 tonnes of potentially harmful chemicals infiltrate aquifers each year, causing detrimental effects on ecosystems and freshwater resources.
The lead author of the study, Associate Professor Federico Maggi, hailing from the University of Sydney’s School of Civil Engineering, indicated that the research has unveiled the astonishing migration of pesticides from their original application sites. In many instances, these chemicals travel vast distances downstream and, often reach the ocean, albeit in much smaller quantities.”
The study further unveiled that nearly 80 percent of the applied pesticides degrade into daughter molecules or byproducts within the soil surrounding the crops. This finding highlights the intricate chemical transformations these substances undergo in their interaction with the environment.
The degradation process of pesticides often follows a complex sequence, forming a ‘cascade’ of molecules that spread into the surrounding atmosphere. Surprisingly, these transformed molecules can persist for extended periods, retaining the potential to be as harmful as the original pesticide itself. A prime example of this phenomenon is glyphosate, which, despite being highly degradable, breaks down into a persistent and toxic molecule called AMPA, as highlighted by Associate Professor Maggi.
Although the study revealed that only a fraction of the pesticides find their way into river systems after their initial application in the fields, once in the water, the majority of active ingredients ultimately make their way to the ocean. This migration to the ocean poses a significant concern as it holds the potential to negatively impact marine wildlife and coral reefs, putting the very foundation of marine and freshwater food chains at risk. The potential consequences of this widespread movement of pesticides in aquatic ecosystems call for urgent attention and measures to safeguard our environment.
“On paper, 0.1 percent leaching into fresh waterways might not sound like much,” said Associate Professor Maggi. “But it only takes a tiny amount of pesticides to have a negative impact on the environment.”
According to the study’s findings, a concerning amount of 730 tonnes of pesticides find their way into rivers annually. Approximately 13,000 kilometers of river channels experience chemical concentrations surpassing safety limits for various aquatic plants and invertebrates, leading to potential repercussions on the ecosystems of these water bodies, although the precise consequences remain inadequately understood.
Dr. Fiona Tang, a water engineering lecturer at Monash University and co-author of the paper, emphasized that the absence of visible pesticide residues in soil and water should not lead to the assumption that they are not present and impacting critical ecosystems on land, rivers, and oceans.
Another co-author, Dr. Francesco Tubiello, Senior Environmental Statistician at the United Nations’ Food and Agriculture Organisation, stressed the urgency of adopting sustainable management strategies. He called for reducing the use of harmful pesticides in agricultural fields and implementing effective monitoring systems under the 2030 Sustainable Development Agenda.
The research team conducted the study using a vast repository of publicly accessible geospatial data.
However, the authors caution that their paper provides a conservative estimate, as not all pesticides were included in the analysis. Legacy pesticides and those utilized in aquaculture, private residences, and public areas were not examined, potentially indicating higher levels of risk exposure for ecosystems and human populations to these chemicals.
